Biofilm growth and the related changes in the physical properties of a porous medium: 1. Experimental investigation

An experimental investigation was conducted to quantify the permeability reduction caused by enhanced biological growth in a porous medium. Studies were conducted using sand‐packed column reactors for which variations in piezometric head, substrate concentration, and biomass measured as organic carbon were monitored in space and time. Methanol was used as a growth substrate. Permeability reductions by factors of order 10⁻³ were observed. The data show that a limit on permeability reduction exists, having a magnitude of 5 × 10⁻⁴ in the present study. The limit on permeability reduction and the existence of high densities of bacteria in substrate depleted zones are explained with an open pore model. Permeability reduction was observed to correlate well with biomass density for values less than about 0.4 mg/cm³, and exhibited independence at higher densities.